INTERBILAYER CHARGE DYNAMICS IN YBA2CU3O6+X

We present optical reflectivity and Raman scattering studies of YBa2Cu3O6+x as a function of doping using c-axis polarized light. The c-axis optical response of YBa2Cu3O7 is characterized by a Drude-like conductivity and an electronic Raman continuum, indicating a weak coupling between adjacent CuO2 bilayers which is mediated by the CuO chains. With reduced doping, the c-axis Drude and continuum responses rapidly decrease, revealing a strong sensitivity of the interbilayer coupling strength to the removal of oxygen from the chain sites. We suggest that interbilayer charge transport in YBa2Cu3O6+x may be governed by carrier scattering from in-plane fluctuations.